For the past twenty years, a number of systems have been developed to provide means for containing pets within a certain predefined area. U.S. Pat. No. 3,753,421 to Peck discloses a system which uses a wire to define the boundary of the area to which the animal is to be restrained. In its most general use, the wire is laid out on the ground or buried a short distance beneath the surface of the ground and then connected to a transmitter system. The transmitter system sets up an electrical field in the wire which determines the boundary of the unit. The pet wears a collar which has a receiver and a stimulus system for providing a stimulus to the pet when the pet moves too close to the wire. Often, the collar contains two stimuli systems, one to give an audio warning to tell the pet that it is approaching the boundary and another to give a shock to further warn the pet that it is too close to the boundary.
This system has enjoyed some success but has a number of limitations in that it is rather expensive to obtain the amount of wire needed for a reasonable area and is time consuming or expensive to bury the amount of wire used. In addition, if the pet is somehow able to go beyond the boundary wire, it will receive a stimulus to keep it away from the wire as it tries to re-enter the desired boundary area. Thus, there is no impetus for the pet to return to the desired area.
U.S. Pat. No. 4,898,120 to Brose sets forth a more sophisticated system in which the parameters of an area in which an animal are to be restrained are determined by evaluating a signal received by a central receiver sent from a transmitter on the animal. This central unit may then transmit a signal to a device worn by the animal to generate a warning shock, sound or the like.
This system enables a more sophisticated determination of the area in which the animal is free to roam and avoids the necessity for exposed wires about the parameter. However, such a system is cumbersome to use.
U.S. Pat. No. 5,06,441 to Weinstein also discloses a wireless system for restricting animals to a defined area. The system of Weinstein uses a transmitting system which generates radio signals to be located in or adjacent an area in which an animal is to be restrained. There is a unit adapted to be worn by the animal which receives the signals from the transmitting system. The collar system has a multiplicity of radio receiver each having a separate receiving antenna.
The system disclosed by Weinstein requires a complexed evaluation of the orientation of the received radio signals. A vector summation is performed on those received signals to determine exactly where the animal is within a particular area. The system requires a large amount of power consumption in the receiver and, therefore, requires recharging or replacement of the battery in the collar every night.
Therefore, there is a need for a wireless pet containment system which is relatively simple to use by the consumer and does not use so much power as to inconveniently require frequent rechargement or replacement of batteries in the pet's collar.
It is an object of the present invention to provide a pet containment system which uses a wireless means to control a pet within a particular area.
It is a further object of the present invention to provide such a system which operates effectively over a reasonably long period of time without frequent replacement or recharging of batteries in a pet collar.